The Radiological Research Accelerator Facility (RARAF), located on the Columbia University Nevis Laboratories campus in Irvington, New York is a National Institute of Biomedical Imaging and Bioengineering biotechnology resource center (P41) specializing in microbeam technology. The facility is currently built around a 5MV Singletron, a particle accelerator similar to a Van de Graaff. The RARAF microbeam can produce with high accuracy and precision: 70-120 keV/μm alpha particles 8-25 keV/μm protons 0.6 μm diameter focused beam spot 10,000 cells/hour throughput History RARAF was conceived by Victor P. Bond and Harald H. Rossi in the late 1960s . Their aim was to provide a source of monoenergetic neutrons designed and operated specifically for studies in radiation biology, dosimetry, and microdosimetry. The facility was built around the 4 MV Van de Graaff particle accelerator that originally served as the injector for the Cosmotron, a 2 GeV accelerator operated at Brookhaven National Laboratory (BNL) in the 1950s and 1960s. RARAF operated at BNL from 1967 until 1980, when it was dismantled to make room for the ISABELLE project, a very large accelerator which was never completed. A new site for RARAF was found at the Nevis Laboratories of Columbia University where its cyclotron was being disassembled. The U.S. Department of Energy provided funds to move RARAF to Nevis Laboratories and reassemble it in a new multi-level facility constructed within the cyclotron building. The new RARAF has been routinely operating for research since mid-1984. RARAF was one of the first three microbeam facilities to be built, and it is the only original microbeam facility still in operation. In 2006 the Van de Graaff was replaced by a 5 MV Singletron from High Voltage Engineering Europa (HVEE) in the Netherlands. Microbeam Development As an NIBIB biotechnology resource center, RARAF is dedicated to developing and improving microbeam technologies. Developments focus on adding and improving imaging techniques to the existing microbeam. Neutron and x-ray microbeams are also in development. Some examples of microbeam developments are listed below. Microbeam lens In order to focus charged particles in the RARAF microbeam, an electrostatic lens consisting of six quadrupole arranged in two triplets with each successive quadrupole rotated by 90° around its axis, is used. Each quadrupole triplet consists of 4 ceramic rods on which gold electrodes were plated. This design ensures alignment of the three quadrupoles in the triplet and allows a small pole-gap and better focusing properties. Subcellular targeting